Hungarian Validation of the Individualized Neuromuscular Quality-of-Life Questionnaire (INQoL) in Adult Patients with Muscular Diseases

Background/Objectives: The Individualized Neuromuscular Quality-of-Life Questionnaire (INQoL) is a widely used measure of quality of life in patients with various neuromuscular diseases. This study aimed to adapt and test the validity and reliability of this measure in Hungarian patients with neuromuscular disease. Methods: According to the widely accepted method of validation, we first translated the original INQoL version into Hungarian, and then a native English speaker translated it back into English to test its validity. Following a pretest procedure, the INQoL was administered to 80 patients with various muscular diseases and 30 age-matched controls. The internal consistency and test–retest reliability were assessed. Concurrent validity was measured using the 36-item Short Form Survey (SF-36) questionnaire. Results: For all INQoL subscales, Cronbach’s alpha was above 0.7, demonstrating the reliability of the subscales. The highest Cronbach alpha value was for the Weakness subscale (0.983) and the lowest for the Treatment subscale (0.794). The intraclass correlation coefficient test values ranged from 0.810 (Treatment) to 0.988 (Pain), indicating excellent test–retest reliability. There was a strong correlation between the SF-36 Physical Function and multiple INQoL subscales, including Weakness (r = 0.754, p < 0.001), Fatigue (r = 0.704, p < 0.001), Activities (r = 0.744) p < 0.001, Independence (r = 0.791 p < 0.001), Body Image (r = 0.714 p < 0.001), and overall Quality of Life (r = 0.742 p < 0.001). Conclusions: Our findings indicate that the Hungarian-language adaptation of the questionnaire possesses adequate reliability and construct validity for assessing the quality of life in patients with muscular disorders.